This invention relates to apparatus for mechanically chopping, shearing or shredding solid materials such as scrap automobile and truck tires; scrap insulated electrical conductors; scrap railroad ties; beverage cans; and other solid waste materials required to be reduced to substantially uniform smaller particulate sizes for efficient permanent disposal, commercial recycling, or other utilization. Typically, systems for such purposes include conveyor means for carrying materials to be processed from ground level to the in-feed of a chopper or shredding machine (which for convenience will hereinafter be referred to as the shredder); a screening (or "classifying") device for receiving the produce from the shredder and passing to discharge product fragments of prescribed sizes; and elevator means for returning oversized products to the shredder mechanism. Machines for similar purposes are disclosed for example in U.S. Pat. Nos. 3,578,252; 3,656,697; 3,727,850; 3,841,570; 3,931,935; 4,134,556; 4,156,508; 4,216,916 and 4,363,450.
Stockpiled waste items of the type referred to typically comprise components, some of which are relatively soft but resilient, and some of which are relatively strong and resilient. Other parts may be brittle, and still others soft and non-resilient. Thus, the products discharged by the shredder typically comprise a heterogeneous mix of relatively large sized curvilinear or concave shaped resilient pieces and relatively small sized solid particulates. The mass "flow" characteristics of such mixtures are quite different from the flow patterns of homogeneous mixtures, and this is especially true when the components of the heterogeneous mix are of different specific gravities.
It is the primary object of the present invention to provide in compact unitized form a machine embodying in improved manner all of the above mentioned essential operative components, so as to be readily movable (such as on skids or wheels) from one operative site to another. Another object is to provide in a machine as aforesaid an improved shredded product classification system employing one or more separately competent screening units of unique construction arranged in vertically stacked relation; each unit being readily removable/replaceable and embodying per se important improvement construction features.